Time Server NIO Example
This example listens for connections and tells callers what time it is. Is a simple, blocking program that demonstrates NIO socket channels (accepting and writing), buffer handling, charsets, and regular expressions.
public class TimeServer {
// We can't use the normal daytime port (unless we're running as root,
// which is unlikely), so we use this one instead
private static int PORT = 8013;
// The port we'll actually use
private static int port = PORT;
// Charset and encoder for US-ASCII
private static Charset charset = Charset.forName("US-ASCII");
private static CharsetEncoder encoder = charset.newEncoder();
// Direct byte buffer for writing
private static ByteBuffer dbuf = ByteBuffer.allocateDirect(1024);
// Open and bind the server-socket channel
private static ServerSocketChannel setup() throws IOException {
ServerSocketChannel ssc = ServerSocketChannel.open();
InetSocketAddress isa = new InetSocketAddress(
InetAddress.getLocalHost(), port);
ssc.socket().bind(isa);
return ssc;
}
// Service the next request to come in on the given channel
private static void serve(ServerSocketChannel ssc) throws IOException {
try (SocketChannel sc = ssc.accept()) {
String now = new Date().toString();
System.out.println("now: " + now);
sc.write(encoder.encode(CharBuffer.wrap(now + "\r\n")));
System.out.println(sc.socket().getInetAddress() + " : " + now);
}
}
public static void main(String[] args) {
if (args.length > 1) {
System.err.println("Usage: java TimeServer [port]");
return;
}
// If the first argument is a string of digits then we take that
// to be the port number
if ((args.length == 1) && Pattern.matches("[0-9]+", args[0]))
port = Integer.parseInt(args[0]);
try {
ServerSocketChannel ssc = setup();
for (;;) {
serve(ssc);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}